1. Field of the Invention
This invention relates to a shaft puller and more particularly to a puller for use in extracting a shaft having a threaded and exposed from a surround structure.
2. Prior Art
In many situations, it is necessary to apply a mechanical advantage to extract a shaft which is tightly fitted or has become frozen within associated surround structure. Such a situation commonly exists with regard to the propeller shaft of an outboard motor. In this structure, the shaft is supported in a motor housing by bearings and retained in position by appropriate retaining structure. One end of the shaft protrudes from the motor housing and receives the outboard motor propeller which is attached to the shaft by engaging a nut on the threaded exposed end of the shaft. With the propeller retaining structure removed from the shaft, the shaft is often very difficult to remove because of corrosion or the tight fit of cooperating structure.
Heretofore, there has been no simple structure for providing a mechanical advantage to extract the propeller shaft. Although pullers of a general nature are available, existing puller structures have not been adaptable to the problem of extracting this type of shaft and has generally been inferior in their own design. For example, a stud bolt puller is disclosed in U.S. Pat. No. 3,727,491 to Buckwalter, issued Apr. 17, 1973. In that structure, a sleeve having an internal threaded bore receives a central member therein. The central member has an internal bore which may be threadably engaged over the threaded end of the stud to be removed. With the central member engaged in the sleeve member and threaded onto the stud, the sleeve member is turned while the central member is maintained stationary. In this way, the central member is turned out of the sleeve member to extract the stud.
This arrangement introduces several problems. First, the sleeve member is rotated relative to the surface in which the stud is lodged. The rotational contact between these two members is undesirable in that damage to the surface can easily occur. Additionally, in its use, the stud extractor must be engaged at two points. The central member must be maintained stationary while the sleeve member is rotated.
In a second application of the Buckwalter extractor, the sleeve member is retained stationary and the central member is backed out of the sleeve member. In this arrangement however, the turning of the central member out of the sleeve member may also result in the unthreading of the central member from the stud. If this occurs, the stud will not be lifted from the block in which it is embedded.
Therefore, a need has arisen for a shaft puller which may be operated by engaging the puller at only one point and which positively extracts the shaft without requiring that any of the elements of the puller be in rotational contact with the shaft surround structure.